Photos taken outdoors often have the sky as their background. However, many photos containing interesting foreground objects are taken under an uninteresting or undesirable sky (e.g., with dreadful weather, woeful style, over-exposed lighting condition, etc.). As such, many users or designers desire to replace the uninteresting sky with another preferred sky. For example, a designer wishes to replace a rainy sky captured in an image with a clear sky.
In some conventional systems, one modifies brightness, contrast, color, etc. of the image in order to obtain a more desired sky view. Such modifications, however, only modify respective global properties of the image and do not offer a replacement sky with desirable sky content.